1. Field of the Invention
The present invention relates to a liquid crystal display panel and a method for fabricating the same, and more particularly, to a liquid crystal display panel that recovers from external forces.
2. Description of the Related Art
In general, a liquid crystal display apparatus is a display device where data signals, including image information, are individually supplied to unit pixels arranged in a matrix form. Light transmittance of the unit pixels is controlled to display a desired image. More particularly, the liquid crystal display device includes a liquid crystal display panel in which the unit pixels are arranged in a matrix form and a driving circuit for driving the unit pixels.
The liquid crystal display panel includes a first substrate on which a thin film transistor array is formed and a second substrate on which a color filter substrate is formed. The first and second substrates are attached to each other, so as to face each other and have a predetermined cell-gap therebetween. A liquid crystal layer is formed within the cell-gap. The first and second substrates are attached to each other by a seal pattern formed along the outer edge of an effective image display area on the substrates. A polarizing plate, a retardation plate and like components are installed on outer surfaces of the first and second substrates. Such a plurality of components are selectively constructed, so as to vary an advancing state of light and a refraction ratio to construct a liquid crystal display device having high brightness and high contrast.
A common electrode and a pixel electrode are formed on the surfaces of the first and second substrates that oppose each other. An electric field to the liquid crystal layer between the common electrode and the pixel electrode. That is, a first voltage is applied to the pixel electrode while second voltage, i.e. ground voltage, is applied to the common electrode such that light transmittance of the unit pixels can be individually controlled. To control the voltage applied to the pixel electrode of the unit pixels, a thin film transistor is formed in each unit pixel and used as a switching device.
Alignment layers are also formed on the opposing surfaces of the first and second substrates over the common electrode and the pixel electrode. The alignment layers are rubbed so that liquid crystal molecules of the liquid crystal layer are aligned into a predetermined direction.
FIG. 1 is a plan view illustrating a related art liquid crystal display panel in which a first substrate having a thin film transistor array and a second substrate having a color filter array are attached to each other. As shown in FIG. 1, the liquid crystal display panel 100 includes an image display unit 113 having a plurality of pixels arranged in a matrix form, a gate pad unit 114 connecting to a plurality of gate lines of the image display unit 113, and a data pad unit 115 connecting to a plurality of data lines. The gate pad unit 114 and the data pad unit 115 are formed at peripheral portions of a first substrate 101. The gate pad unit 114 on the first substrate is not overlapped by the second substrate 102. The gate pad unit 114 supplies scanning signals from a gate driving unit to the gate lines of the image display unit 113. The data pad unit 115 supplies image information from a data driving unit to the data lines of the image display unit 113. The data lines receiving the image information and the gate lines receiving the scanning signals are disposed such that the data lines and the gate lines orthogonally cross each other on the first substrate 101. A thin film transistor (not shown) and a pixel electrode (not shown) are formed in each unit pixel defined by the crossing data lines and gate lines.
A black matrix (not shown) is formed on the second substrate 102 corresponding to the gate lines, data lines and the thin film transistors. A plurality of color filters (not shown) corresponding to each unit pixels is formed on the second substrate 102 within the black matrix. In addition, a common transparent electrode corresponding to the pixel electrode is formed on the second substrate 102.
The first substrate 101 and the second substrate 102 are attached by a sealant 116 formed at the periphery of the image display unit 113. Spacers are used to maintain a constant cell-gap between the first substrate 101 and the second substrate 102. The spacers can be ball spacers, such as glass beads or plastic beads, that are dispersed at random between the first substrate 101 and the second substrate 102. However, as liquid crystal display panels have grown in size in recent years, it has becomes more difficult to maintain a precise and uniform cell-gap due to clumping of the ball spacers. Such clumping results in poor picture quality. Therefore, in the case of a large liquid crystal display panel 100, no ball spacers are used. Instead, column spacers or patterned spacers are used that are fixed to either the first substrate 101 or the second substrate 102.
FIG. 2 is a cross-sectional view illustrating a related art liquid crystal display panel on which column spacers are formed. As shown in FIG. 2, a liquid crystal display panel 200 includes a first substrate 201 having a thin film transistor array and a second substrate 202 having a color filter array that are attached to each other, so as to face into each other. Column spacers 210 are formed on the second substrate 202, thereby maintaining a cell-gap between the first substrate 201 and the second substrate 202. The column spacers 210 are affixed to the second substrate 202 such that they appropriately contact the surface of the first substrate 201 when the first substrate 201 and the second substrate 202 are attached to each other.
In the case where the column spacers 210 are affixed to the second substrate 202 for appropriate contact with the surface of the first substrate 202 as described above, a problem arises. More specifically, if the second substrate 202 is shifted across the column spacers 210 due to a compression by an external force, such as someone touching the display screen, it takes long time for the second substrate 202 to return to the original position because there is a large frictional force in the surface contact between the column spacers 210 and the first substrate 201. Accordingly, touch smears or compression deficiencies are observed in images of the liquid crystal display panel 200 long after the external force is no longer applied, thereby degrading display quality.